Reporting at the annual meeting of the American Chemical Society, a group of researchers lead by Tsanangurayi Tongesayi, an associate professor of chemistry at Monmouth University in New Jersey announced the results of their analysis of rice from Asia, Europe and South America. The imports, which currently make up about 7% of rice consumed in America, contained higher than acceptable levels of lead.

The levels ranged from six milligrams/kilogram to 12 milligrams/kilogram; factoring in average consumption, that added up to estimated lead exposure levels 30 to 60 times greater than the Food and Drug Administration’s (FDA) provisional total tolerable intake (PTTI) levels for children and 20-40 times greater than the standard exposure levels for adults.

The agency’s PTTI represent the maximum level of contaminant exposure before potentially toxic or adverse health effects might occur. “Now, according to the FDA, for chemical toxicants to cause a health effect, they have to be ten times the PTTI. Our calculated exposure levels were two to 12 times higher than ten times the PTTI. Meaning, they can cause adverse health effects,” says Tongesayi.

Because Asian populations in the U.S. tend to consume the most rice, the researchers also calculated exposure levels for these groups, and estimated that Asian infants and children in the U.S. could be exposed to lead at 60 to 120 times higher than the FDA’s PTTI. And young children under six years old can be especially vulnerable to lead poisoning, which can impair mental and physical development and, if the exposure is sustained, can be fatal.

“The thing is that is rice becoming a staple food for a larger percentage of the population,” says Tongesayi. He says their calculations are also conservative, since they were basing consumption on the daily recommended servings. It’s likely that many people consume more than what’s recommend in a given day– or week.

Rice from Taiwan and China contained the highest levels of lead, although rice from Italy, India, Thailand, Bhutan and the Czech Republic also contained levels higher than the PTTI. The researchers are continu8ing their sampling with rice from Pakistan and Brazil as well as other countries. With the increase in imports, Tongesayi says rice from these countries are not only appearing in ethnic and specialty restaurants and stores, but also in mass market grocery store and supermarket chains.

While lead exposure can negatively affect cognitive development and performance in kids, adults with high lead exposure can also experience problems with blood pressure, heart disease and calcium deficiency. Tongesayi’s team believes the rice became contaminated during growing and harvesting. “Processing can potentially add some contaminants, but from what we studied, it seems that the contamination is coming from contaminated soils and contaminated irrigation waters,” he says.

The findings come after concerns about arsenic contamination in rice as well, but, say the researchers, shouldn’t discourage people from eating rice. Instead, Tongesayi and his colleagues hope their work increases consumer awareness about food safety and prompts more stringent oversight of imported products. “We just hope that our results will inform public policy and will be used to create stricter regulations on lead in rice, or be used to come up with eating advisories like [those] with mercury in fish,” he says. “It is a bit difficult because people can’t stop eating it, and that is not what we are trying to say, but we want people to be aware that some of the foods they are eating are tainted with these toxic chemicals. You can eat less on a given day.”

Tongesayi only studied imported rice so the findings aren’t applicable to rice grown in the U.S. While the U.S. is a major exporter of rice, imports of rice and rice flour have increased by over 200% since 1999, raising concerns about the safety of the products. Noah Bartolucci, a spokesperson for the FDA, said to BBC News that the agency “plans to review the new research on lead levels in imported rice released today”. Any adverse effects from contaminants will need to be weighed against the grains’ nutritional benefits. Yet, such results should alert regulatory agencies to be vigilant as global markets continue to expand and imports increase.